The field of the invention is indicator lights used on control panels for electrical equipment.
Indicator lights for control panels take many forms. Some indicator lights are separate devices, often referred to as "pilot lights", and others form part of electrical components such as push button switches and selector switches. The indicator light may merely illuminate an area on the control panel, or it may illuminate alpha-numeric characters or other symbols which convey a message to a human observer. It is important that the indicator disperse light relatively uniformly, and over a wide angle, so that the human operator may receive an accurate indication from any viewing angle.
Prior indicator lights typically attempt to achieve these objectives in one of two ways. First, they may use glass lenses which focus the light in a desired pattern, or second, they may employ a transparent or translucent light diffuser which scatters the light from the indicator in a random fashion. Glass lenses are expensive and neither of these approaches eliminates uneven illumination, or "hot spots", due to the reflection of light off the back surface of the lens or diffuser. These problems are exacerbated when physical constraints are placed on the location of the indicator light in devices such as push button switches.